1. Field of the Invention
The present invention relates to the manufacture of aircraft track-cans or the like.
2. Description of the Related Art
Aerodynamic flying control surfaces such as slats and flaps are often powered by a system of rotary actuators and rack and pinions located in the leading edge of aircraft wings. The racks are arcuate to provide the required flap or slat movement and must extend into the main wing structure when retracted. It is quite common, particularly on large modern airliners, for fuel to be contained within the main wing structure. Accordingly, the wing is constructed in the form of a sealed container and means are provided to isolate the racks of the rack and pinions used to drive the flaps and slats from the fuel. It is known to provide apertures in the leading wall of the wing structure through which the racks may pass into the interior of flanged cans, known as track-cans, sealingly surrounding the apertures inside the wing structure.
In order to keep the dimensions of the track-cans small to save weight and avoid wasting fuel space, the track-cans are preferably made generally cylindrical but with arcuate longitudinal axes conforming to the arcuate movement of the racks they are to contain. The manufacture of track-cans thus shaped has hitherto comprised forming the cans (for example, by drop hammering) in two identical halves, split along the longitudinal axis, i.e. along the arc of the rack when retracted. After forming the halves, a flange is present around the periphery of each of the halves which must be removed before welding them together. This operation can lead to inaccuracies in the component, and after removal of the flange, the halves are prone to distortion when handled. The two halves are initially tack welded together (in an attempt to prevent relative movement therebetween) and subsequently seam welded to form the required track-can. The seam welding process is difficult to perform manually and, furthermore, is not readily automated because of the long and arcuate nature of the seam. Further, formation of the two halves of the track-can requires a tool of unconventional shape but relatively high tolerance.